Heat Treated Silica for Improved Dentifrice
Heat treated silica materials are disclosed, together with methods of making such materials, and dentifrice compositions containing the heat treated silica materials. The heat treated silica materials can contain trace amounts of cristobalite, typically less than 1 wt. %, and the heat treated silica materials often have a loss on ignition of less than about 2 wt. %.
1 . A dentifrice composition comprising a polyvinylpyrrolidone-hydrogen peroxide complex and a precipitated silica material, wherein:
the precipitated silica material comprises from greater than 0 to less than about 1 wt. % cristobalite; and
the precipitated silica material is characterized by a loss on ignition of less than about 2 wt. %.
2 . The composition of claim 1 , wherein the precipitated silica material comprises from greater than 0 to less than about 0.1 wt. % cristobalite.
3 . The composition of claim 1 , wherein the precipitated silica material is characterized by a loss on ignition of less than about 1 wt. %.
4 . The composition of claim 1 , wherein the precipitated silica material is further characterized by:
a BET surface area in a range from about 20 to about 60 m 2 /g;
an oil absorption in a range from about 70 to about 120 cc/100 g; and
a Brass Einlehner abrasion value in a range from about 4 to about 20 mg loss/100,000 revolutions.
5 . The composition of claim 1 , wherein the precipitated silica material is further characterized by a Brass Einlehner abrasion value in a range from about 5 to about 10 mg loss/100,000 revolutions.
6 . The composition of claim 1 , wherein the precipitated silica material is further characterized by:
a peak transmittance in glycerine at a refractive index greater than 1.45; and/or
a peak transmittance in sorbitol at a refractive index greater than 1.45.
7 . The composition of claim 1 , wherein the precipitated silica material is further characterized by:
a peak transmittance in glycerine at a refractive index in a range from about 1.45 to about 1.46; and
a peak transmittance in sorbitol at a refractive index in a range from about 1.45 to about 1.46.
8 . The dentifrice composition of claim 1 , having a tube stability at 60° C. of at least about 5 days.
9 . The dentifrice composition of claim 1 , having a tube stability at 60° C. in a range from about 7 days to about 50 days.
10 . A method for preparing a dentifrice composition, the method comprising:
(a) heat treating a precipitated silica material at a temperature and for a period of time sufficient to form a heat treated silica material comprising from greater than 0 to less than about 1 wt. % cristobalite, the heat treated silica material characterized by a loss on ignition of less than about 2 wt. %; and
(b) contacting the heat treated silica material with a polyvinylpyrrolidone-hydrogen peroxide complex and other ingredients to form the dentifrice composition.
11 . The method of claim 10 , wherein the heat treated silica material comprises from greater than 0 to less than about 0.1 wt. % cristobalite, and is characterized by a loss on ignition of less than about 1 wt. %.
12 . The method of claim 10 , wherein the method comprises heat treating the precipitated silica material at a temperature of from about 650° C. to about 1000° C. for a period of time from about 20 minutes to about 20 hours to form the heat treated silica material.
13 . The method of claim 10 , wherein the method comprises heat treating the precipitated silica material at a temperature of from about 700° C. to about 950° C. for a period of time from about 14 to about 18 hours to form the heat treated silica material.
14 . The method of claim 10 , wherein the dentifrice composition has a tube stability at 60° C. of at least about 10 days.
15 . The method of claim 10 , wherein the dentifrice composition has a tube stability at 60° C. in a range from about 5 days to about 40 days.
16 . The method of claim 10 , wherein the dentifrice composition has a tube stability at 60° C. that is greater than a tube stability at 60° C. of a dentifrice composition containing the precipitated silica material.
17 . The method of claim 10 , wherein the dentifrice composition has a tube stability at 60° C. that is at least 5 times greater than a tube stability at 60° C. of a dentifrice composition containing the precipitated silica material.
18 . A precipitated silica material comprising from greater than 0 to less than about 1 wt. % cristobalite, and characterized by a loss on ignition of less than about 2 wt. %.
19 . The precipitated silica material of claim 18 , wherein the precipitated silica material comprises from greater than 0 to less than about 0.1 wt. % cristobalite, and wherein the precipitated silica material is characterized by a loss on ignition of less than about 1 wt. %.
20 . The precipitated silica material of claim 18 , wherein the precipitated silica material is further characterized by:
a BET surface area in a range from about 20 to about 60 m 2 /g;
an oil absorption in a range from about 70 to about 120 cc/100 g;
a Brass Einlehner abrasion value in a range from about 4 to about 20 mg loss/100,000 revolutions;
a peak transmittance in glycerine at a refractive index in a range from about 1.45 to about 1.46; or
a peak transmittance in sorbitol at a refractive index in a range from about 1.45 to about 1.46; or
any combination thereof.